Drug passed on to fish boosts their confidence

Brady Dennis

If it's a wild European perch exposed to a popular anxiety medication, chances are it wanders away from the safety of its group and devours food quicker than its peers - behaviour that could have profound consequences, says a forthcoming report in the journal Science.

Researchers from Umea University, in Sweden, examined how perch behaved when exposed to oxazepam, a drug commonly used to treat anxiety disorders in humans.

The scientists exposed the fish to concentrations of the drug similar to those found in waters near densely populated areas of Sweden.

Advertisement

The result?

''Normally, perch are shy and hunt in schools. This is a known strategy for survival and growth,'' Tomas Brodin, an ecologist and lead author of the Science article, said. ''But those who swam in oxazepam became considerably bolder.'' They ''lost interest in hanging out with the group''.

''We think it's working through stress relief on the fish,'' Professor Brodin said. ''It removes the fear of being eaten.''

The researchers said such behaviour, coupled with the tendency to eat faster, could lead to ecological changes in the real world. For example, if they consumed more plankton, it could lead to an increase in algae.

Professor Brodin and his colleagues noted that residue from a ''veritable cocktail of drugs'' could be found in waterways worldwide.

The US Food and Drug Administration has said that the main way that drugs enter water systems is by passing through individual patients.

''The solution to this problem isn't to stop medicating people who are ill,'' said Jerker Fick, a co-author of the Science report, ''but to try to develop sewage treatment plants that can capture environmentally hazardous drugs.''